With permission from RT, I'm going to define some terms and outline what I will defend in this debate.

Useful Definitions

Bohmian mechanics-- a non-relativistic Galien invariant for the motion of point particles formed on a configuration of space. His equations give us the configuration of the system of particles, the trajectory of the particles given the initial data, the equation for the motions of the particle, as well as the universal wave-function: an equation governing the trajectory of all particles.

Verification principle-- the doctrine that nontautologous statements are meaningful only if it is in principle possible to establish empirically whether they are true or false

Epistemology-- the branch of philosophy that studies knowledge

Ontology-- the branch of metaphysics dealing with the nature of being (existence)

Introduction and Outline

In this debate, I will be defending three contentions. My first contention will be that Bohm's mechanics is empirically equivalent with standard quantum mechanics, so there is no way to falsify it without disproving quantum mechanics itself. My second contention will be that none of RT's arguments to serve to establish the implausibility of Bohmian mechanics. My third contention will be that, even though all interpretations of quantum mechanics are empirically equivalent, we have good philosophical reasons to affirm Bohm's interpretations.

I look forward to a challenging and interesting debate with Rational Thinker. I will try to keep my arguments relatively non-technical to make this an easier debate to judge. I hope that RT follows me in doing this.

I suppose my opponent's definitions are sufficient. However, I would like to add to the definition of Bohmian mechanics:

"Bohmian mechanics, which is also called the de Broglie-Bohm theory, the pilot-wave model, and the causal interpretation of quantum mechanics, is a version of quantum theory discovered by Louis de Broglie in 1927 and rediscovered by David Bohm in 1952. It is the simplest example of what is often called a hidden variables interpretation of quantum mechanics."[1]

In this debate, I will be arguing that it is false that Bohmian mechanics is experimentally equivalent to standard Quantum Mechanics, and that some interpretations can be ruled out, or made implausible by experiment. I will then be arguing that Bohmian mechanics violates Occam's Razor, and is most likely false due to recent experiments.

The Current State Of Bohmian Mechanics In Physics

This is not an argument in favor of the resolution, so Pro cannot call me out on an Ad Populum fallacy. I am just potentially bulking up my argument by showing the current support the interpretation my opponent endorses has in physics.

The poll carried out by Maximilian Schlosshauer, Johannes Kofler, and Anton Zeilinger shows that barely anybody accepts Bohm mechanics, while the most support goes to the Copenhagen interpretation. This survey was only done with 33 participants, but I highly doubt if the sample size was bigger a major difference would appear.

Can Certain Experiments Rule Out, Or Make Implausible Certain Interpretations?

My opponent may argue that all interpretations of quantum mechanics are empirically equivalent. Is this true? Well, of course not. If this was true, then we never would have known than Bohm's original interpretation (that there were local hidden variables) was false due to violations in Bell's Inequalities. However, these experiments ruled out that particular interpretation[2]. There is no reason to think this couldn't be the case for non-local hidden variables as well (I will actually argue that it is the case later on). Therefore, we know that certain interpretations can be ruled out by experiment. Physicist Victor Stenger drives the point home:

"Now, after a series of precise experiments, the issue has been decided: the Copenhagen interpretation of Quantum Mechanics has been convincingly confirmed, while the most important class of hidden variables have been ruled out." - Victor Stenger[3]

Therefore, the idea that all interpretations of quantum mechanics are experimentally equivalent is false, and there is no reason to think current Bohmian mechanics makes the exact same predictions as the other interpretations (it doesn't). As far as other interpretations are concerned, Max Tegmark even came up with a thought experiment, which could show whether the Many-World's interpretation was true or not called "quantum suicide"[4]. Even more concrete, R. Plaga came up with an idea to test the Many Worlds Interpretation in the paper "Proposal for an experimental test of the many-worlds interpretation of quantum mechanics"[5]. There are ways to test certain interpretations, and they are not all necessarily experimentally equivalent.

Why Is Bohmian Mechanics Probably False?

P1: If Bohmian Mechanics is true, realism is true P2: Realism is not true C: Therefore, Bohmian Mechanics is not true

The argument is valid Modus Tollens. But why accept the premises?

Defense of P1

Bohmian mechanics predicts realism:

"Bohmian mechanics insists on realism..."[6]

"Bohmian mechanics is realist."[7]

We know Bohmian mechanics is realist because it denies the objective collapse of the wave-function upon measurement.

"[I]nterpretations such as that of de Broglie and Bohm in which no collapse occurs..." - P.R. Holland[8]

If there is no wave-function collapse, then particles have definite positions when not observed; and realism (or "naive" realism) is true[9]. This is what Bohmian Mechanics embodies. I don't think my opponent will object to P1 of the argument, because it is well known and not controversial that Bohmian mechanics is realist. The issue, it seems, will be surrounding P2.

Defense of P2

Violations of Leggett's inequalities by Anton Zeilinger in 2007 falsified a broad range of non-local hidden variables and realistic pictures[10]:

"Now physicists from Austria claim to have performed an experiment that rules out a broad class of hidden-variables theories that focus on realism."[10]

However, there were still some loopholes. These loopholes can be considered refuted by the before-before experiment, which is explained in further detail in the paper "Nonlocal 'realistic' Leggett models can be considered refute by the before-before experiment" by Antoine Suarez[10]. So, non-local realism is done for, thus, Bohmian mechanics is done for. If that is not enough, in 2012 a huge team of scientists confirmed the closing of all loopholes for realism:

"Our work disproves the view that a quantum system might, at a certain point in time, appear definitely as a wave or definitely as a particle [before measurement]." - Anton Zeilinger[12]

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It seems that because realism is so problematic in modern physics, and experiments keep ruling it out; we should reject realism. But Bohmian mechanics is realist (it rejects wave-function collapse upon observation). Thus, Bohmian mechanics is probably false.

Richard Feynman And The Uncertainty Principle

"Heisenberg recognized that if it were possible to measure the momentum and the position simultaneously with a greater accuracy...quantum mechanics would collapse. So he proposed that it must be impossible." - Richard Feynman[13]

Nobel Prize winner Richard Feynman makes a good argument in favor of the Uncertainty Principle, and against hidden variables. Imagine that there are hidden variables, and that an electron in some experiment has some internal variables that are not known, which determine the electron's trajectory given a set of initial conditions (similar to how it is in classical mechanics). However, since these hidden variables are not observed, grouping it with a classical system would entail that the effect was not changed. If these inner variables force the electron to go through the upper slit and land at a certain place on the opposite screen, and some other location for the lower screen, then the probability must neccesarily be the sum of two Gaussian like peaks: which self-evidently doesn't agree with observation.

Occam's Razor And Ad Hocness

This section alone is sufficient to establish the resolution. We have a clear prima facie case interderministic interpretations, as Quantum Mechanics appears inherently indeterministic. The idea that there are non-local "hidden variables" really making the process deterministic is worse than divinely hidden fossil theories from creationists! We wouldn't doubt evolution because of the possibility of God planting fossils to make it look "as if" evolution happened, so why doubt indeterministic interpretations because of the possibility of hidden variables making it look "as if" there is randomness? We wouldn't. Even though it is possible, it is not probable. Thus, Bohmian mechanics is improbable because it is Ad Hoc and violates Occam's Razor.

Conclusion

I showed that interpretations of Quantum Mechanics can be either ruled out, or confirmed by experiment and that they do not all make the same predictions. I showed that local hidden variables have being ruled out and this falsified older interpretations of Quantum Mechanics, so there is no reason to believe that we cannot rule out non-local hidden variables as well. Also, if interpretations all inherently make the same predictions, then there wouldn't be so many papers discussing how to test interpretations.

I showed that Bohmian Mechanics is realist, and that realist interpretations are not compatible with modern experiments. Thus, it is probably false. Basically, violations in Bell's inequalities shows there are no local hidden variables, and violations in Leggett's inequality demonstrate that there aren't non-local hidden variables. Of course, there were some loopholes, but they have been closed by the before-before experiment (and experiments as recent as last year). I also showed that the Uncertainty Principle is not just epistemic, and that Bohmian mechanics is Ad Hoc and violates Occam's Razor.

The resolution has been established. Bohmian mechanics fails to be compatible with observation, and should be rejected.

Bohmian mechanics is empirically equivalent with standard quantum mechanics. The article “Bohmian Mechanics”, published in the journal of Compendium of Quantum Physics, states that “in a world governed by Bohmian mechanics, observers see the same statistics for experimental results as predicted by quantum mechanics.” [1] The physicist Brian Greene, who is not a Bohmian, writes that "This {Bohm's mechanics} approach agrees fully with the successful predictions of standard quantum mechanics...."[2] The book Einstein, Relativity, and Absolute Simultaneity also notes that "Bohmian quantum mechanics is mathematically consistent and consonant with all experimental results..". [3]

Note that this is not the same thing as saying “no experiment has falsified Bohm’s mechanics yet”. Rather, it’s inherent to the mathematics in his mechanics that it makes the same predictions as quantum mechanics. This makes it fundamentally impossible to falsify Bohm’s mechanics without getting rid of QM itself. The Stanford Encyclopedia of Philosophy states that “Secondly, and this is crucial to the fact that Bohmian mechanics is empirically equivalent to orthodox quantum theory, the right hand side of the guiding equation is J/ρ, the ratio of the quantum probability current to the quantum probability density. “[4] It’s not a matter of the current state of scientific research that Bohm’s mechanics is equivalent with standard quantum mechanics, but an inherent fact about his mathematics.

None of what RT said in his second section even touches this first contention. For the first contention, I don’t need to prove that every interpretation of quantum mechanics is empirically equivalent, but only Bohm’s. However, it’s worth noting that he’s made some errors in reading his sources. He mentions quantum suicide as a way of empirically falsifying an interpretation of quantum mechanics. His own sources disagrees with this interpretation. Source 4 states that quantum suicide is a “thought experiment” and that “In­stead of using the scientific method -- investigating empirical evidence -- to study the quantum level, physicists must use thought experiments”. Offering quantum suicide as a way of empirically demonstrating an interpretation to be false is therefore a misunderstanding, because it’s a philosophical argument. His source from R. Plaga doesn’t entail that all interpretations aren’t empirically equivalent. It just just mean that, upon falsifying many worlds, you would have taken the rest of QM down with it.

Contention Two: None of RT's arguments to serve to establish the implausibility of Bohmian mechanics.

Legget’s inequalities have nothing to do with Bohmian mechanics; This would be apparent if RT had read the entirety of Zeilinger’s paper, which he cites.

“"It is clear that other classes of non-local theories, possibly even fully compliant with all quantum mechanical predictions, might exist that do not have this property when reproducing entangled states. Such theories may, for example, include additional communication [23] or dimensions [24]. A specific case deserving comment is Bohm's theory [25]. There the non-local correlations are a consequence of the non-local quantum potential, which exerts suitable torque on the particles leading to experimental results compliant with quantum mechanics. In that theory, neither of the two particles in a maximally entangled state carries any angular momentum at all when emerging from the source [26]. Incontrast, in the Leggett model, it is the total ensemble emitted by the source that carries no angular momentum, which is a consequence of averaging over the individual particles' well defined angular momenta.”[5] [Bold text mine]

RT claims that Bohmian realism has been falsified, and cites a paper by Suarez. However, that very paper says that Bohm’s definition of realism has not been falsified:

“Models assuming that the “realistic" mechanism happens in a single preferred frame even in relativistic experiments with devices in motion, are not refuted by the before-before experiment” [6]

Bohm’s mechanics involves a single preferred frame: “If then, we allow for causal connections between the events situated at A and B, the EPR experiment implies the existence of absolute simultaneity and an ether frame. And, in fact, such a theory exists in the form of the de Brogile-Bohm pilot wave model”. [7]

Ergo, its realism is not refuted by the before-before experiment. Furthermore, Suarez’s paper is about Legget’s inequalities, which have nothing to do with Bohm.

He cites a quantum eraser experiment which was supposed to show that a quantum system can’t appear definitely as a wave of a particle. Zeilinger’s argument is that a quantum system can’t appear definitely as a wave of a particle because that would require faster than light communication, which violates Einstein’s general theory of relativity. This means that his argument only works if you accept Einstein’s general theory of relativity, which is based on the Minkowski interpretation of special relativity. However, this interpretation of special relativity has been falsified by Alain Aspect’s experiments with Bell’s inequalities. Writing about these experiments, the physicist S. J. Prokhovnik says that “‘’The notion of non-local causality, discussed by Bell, requires a criterion of absolute simultaneity which has some absolute significance: it is seem that a cosmological basis for a universal measure of cosmic time resolves this problem...’’.[8] Zeilinger’s argument only works if you accept the Minkowski interpretation of special relativity, which has been experimentally falsified.

RT's argument from Richard Feynman seems to misunderstand Bohm's mechanics, because it doesn't deny the uncertainty principle. Bohm agreed that observers could only have limited knowledge about position and velocity [9]. Bohm's only difference was stating that the uncertainty principle was epistemological (it's a limit on what us humans can know), rather than ontological (it relates to a fact about reality that things don't have an absolute position or velocity until they're measured). Arguing for the uncertainty principle, therefore, does nothing to undermine Bohm's mechanics. RT has also failed to explain why Feynman's argument relates to Bohm's mechanics at all, so I'll end this point on the grounds that the argument is too poorly explained to answer.

Occam's razor is an epistemological device which states that the simplest theory should take precedence. I'm thankful RT brought this up, because it serves as an argument for Bohmian mechanics. By contention one, Bohm's interpretation is equal with orthodox QM. By Occam's razor, we should favor the simplest interpretation. The Copenhagen interpretation, which RT supports, denies that things have position or velocity absent of measurement, and thus goes against our intuition. As Einstein commented, "Do you really think the moon isn't there if we're not looking at it?". On the other hand, Bohm treated this as a limit on what we can know rather than what is, so the moon really is there even if we're not looking at it. Copenhagen goes against our intuitions about reality, while Bohm's does not, so it is a simpler theory.

An ad hoc hypothesis is a hypothesis which is changed to fit the data, saving it from being disproven. What part of Bohm's mechanics was changed in order to save it from being disproven? RT never tells us, so this argument doesn't work either.

Contention Three: Philosophical arguments for Bohm's mechanics

The verification principle is the principle which states that nontautologous statements are meaningful only if it is in principle possible to establish empirically whether they are true or false. This is the entire basis for the Copenhagen interpretations view on the uncertainty principle. Heisenberg originally viewed his uncertainty principle as a limit on knowledge, just like Bohm. [10] However, he was convinced by Bohr to view it as ontological, and not just a limit on human knowledge. This was the birth of the Copenhagen interpretation of quantum mechanics.

However, the verification principle is now widely accepted to be false. Tyler Burge, professor of philosophy at UCLA, once said that the central event in philosophy during the 21st century was ‘the downfall of positivism and the re-opening of discussion of virtually all the traditional problems of philosophy’’.[11] One problem, for example, is that there is no empirical way of justifying the verification principle, so it refutes itself.

Copenhagen was based on a flawed philosophy, making it philosophically inferior. Bohm recognized that the uncertainty principle was epistemological, not ontological, thereby taking verificationism out of physics. This makes Bohm's mechanics philosophically superior to Copenhagen.

Conclusion

Thank to RT for this engaging debate, and I wish him luck in his next round.

Bohmian Mechanics Is Not Experimentally Equivalent To Standard Quantum Theory

It is simply not true that the predictions Bohmian mechanics makes are necessarily experimentally equivalent to orthodox quantum theory. In the paper "Is the de Broglie-Bohm interpretation of quantum mechanics really plausible?" By Physicist Kurt Jung, he states:

“[P]redicted properties [in the Bohmian interpretation] of atoms and molecules are in conflict with experimental findings.” – Kurt Jung[1]

Physicist Ilja Schmelzer drives this point home:

“... it is not true that the de Broglie-Bohm theory gives the same predictions in general. It can be arranged to do so in the case of one spinless particle. But in the real quantum theories we find relevant today, such as quantum field theory, de Broglie-Bohm theory cannot be constructed to match probabilistic QFT exactly, and one can see that its very framework contradicts observable facts.” - Ilja Schmelzer[2]

Even if the math is the same, the idea that Bohmian mechanics inherently experimentally equivalent is absurd. People are thinking of experiments right now that could test whether a wave-function actually collapses or not. P. R Holland published a paper called "Testing Wave-Function Collapse"[3]. The abstract of the paper is as follows:

“The technique of measuring the wavefunction of a single system suggests a method for distinguishing between epistemological interpretations of quantum mechanics which postulate wavefunction collapse and ontological interpretations such as that of de Broglie and Bohm in which no collapse occurs.” - P.R Holland [3]

If the wave-function collapses for real, then interpretations like the Copenhagen interpretation remain unscathed. However, this would spell death for the Bohmian mechanics. Therefore, it should be clear by now that Bohmian mechanics can be ruled out by experiment without necessarily harming other interpretations.

As far as the paper from R. Plaga, it only deals with the Many-Worlds interpretation. If the test proposed came up negative for that interpretation; other interpretations would not be harmed.

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The irony of my opponent’s argument here is that if it holds; he admits that his “hidden variable” theory is unfalsifiable. However, as Con rightly notes himself:

“[T]he hypothesis is fundamentally bad, as it cannot be falsified.” – Sargon[4]

If “hidden variables” are really unfalsifiable as my opponent claims (which follows from his notion that we cannot disprove Bohmian mechanics without disproving the Copenhagen interpretation), then my opponent admits his that his hypothesis involving “hidden variables” is fundamentally bad. This is because we can explain the data without that unnecessary assumption; it is improbable.

“Violations of Leggett's inequalities by Anton Zeilinger in 2007 falsified a broad range of non-local hidden variables and realistic pictures. However, there were still some loopholes.” – Me

I left open the clear possibility that Bohmian mechanics wasn’t harmed by this particular experiment.

Antoine Suarez And The Before-Before Experiment

My opponent is correct about the before-before experiment. I failed to take into account the fact that Bohmian mechanics entails a single preferred frame in context, which does seem to get passed my objection.

Quantum Erasure With Causally Disconnected Choice

My opponent denies that this experiment hurts Bohmian mechanics by claiming that the interpretation of Special Relativity that this argument against Bohmian mechanics depends upon (Minkowskian spacetime) is false. He cites the Alain Aspect’s experiments with Bell’s inequalities which show instantaneous interaction, which seems to hurt the Minkowskian framework which predicts that there is no absolute simultaneity. However, this is not necessarily the case if entangled particles are entangled across time. A recent experiment by E. Megidish, A. Halevy, T. Shacham, T. Dvir, L. Dovrat, and H. S. Eisenberg shows this to be the case in the paper "Entanglement Between Photons that have Never Coexisted"[5].

Since this experiment shows entangled particles that are entangled across time, the idea that quantum entanglement harms the way we usually think about Special Relativity is false. The Minkoskian interpretation should be accepted over other views because any physical system whatsoever will exhibit the exact same contraction. This would be extremely unlikely if Minkoskian spacetime was false. In the paper "Presentism and Relativity", Yuri Balashov and Michael Janson write:

"The universality of the behavior of the rod suggests that space and time are Minkowskian. Length contraction is part of the normal spatiotemporal behavior of systems in Minkowski space-time." - Yuri Balashov and Michael Janson[6]

Additionally, the idea that space and time are not married in reality violates the symmetry principles of Earman (which are taken seriously in science).

This particular experiment by Anton Zelienger shows that Bohmian mechanics is probably false.

--

The team’s chief result doesn’t necessarily depend on interpretations of Special Relativity anyway:

They show in the paper that no naïve realistic picture (this includes Bohmian mechanics, as it denies wave-function collapse as real) is combatible with the experiment because any hidden variables would have to ‘know’ what choices the experimenter would choose before the experiment took place, and change the quantum states accordingly; which is, of course, seemingly impossible without further fundamental grounding for such an outrageous mechanism. Therefore, Bohmian mechanics should be rejected due to this experiment regardless of interpretations of Special Relativity.

Richard Feynman And The Uncertainty Principle

My opponent completely misunderstands the argument here. When I said that Feynman argues for the Uncertainty Principle, I meant that he argues for it being ontological and not just epistemological. This should have been evident, as the whole argument is about the problem with hidden variables. Also, in my summary of my last round I said:

“I also showed that the Uncertainty Principle is not just epistemic.” – Me

I was referring to Richard Feynman’s argument. Therefore, my opponent hasn’t actually addressed Richard Feynman’s argument. His rebuttal is based on a misunderstanding regarding the assumption that when I was talking about an argument for the Uncertainty Principle; I wasn't speaking about its ontology (I was however).

“It states that among competing hypotheses, the hypothesis with the fewest assumptions should be selected.”[8]

Claiming that there are “hidden variables” making it look “as if” the wave-function collapses, is like saying that evolution is false, and this “hidden variable” Diety is planting fossils and DNA making it look “as if” evolution is true. It’s an unnecessary assumption and should be rejected. Con mentions Einstein’s intuition that the moon is there when nobody looks. However, in some interpretations of the Copenhagen interpretation, it is the measurement device which causes collapse of a wave-function (not conscious observation)[9]. Therefore, as long as there are classical systems interacting with quantum systems; the moon is still there. Either way, this type of intuition doesn’t trump a prima facie case like mine. It truly seems like the wave-function collapses (this is just some of the weirdness of quantum mechanics commonly accepted). Thus, we should believe it lacking any defeaters.

My argument regarding Occam’s Razor and Ad Hocness stands.

My Opponent’s Philosophical Argument

My opponent hasn’t presented any argument in favof Bohmian mechanics being probably true. Con is only trying to undermine the Copenhagen interpretation. Even if that interpretation is false, that doesn’t mean Bohmian mechanics is probably true; that is a non-sequitur fallacy. Many-Worlds could be true, or the Ghirardi–Rimini–Weber interpretation (there are tons of interpretations). Since the Copenhagen interpretation being false wouldn’t automatically mean that Bohmian mechanics is probably true; this argument from Con can't hold up his burden.

My opponent’s argument does fail though, as it only tries to undermine the notion that the Copenhagen interpretation is necessarily ontological based on the verificationalism which implies it. It doesn’t follow from this that the Uncertainty Principle is probably epistemological (Con made this odd leap) just because he undermined one reason to believe it is true that isn’t even necessary for reasonable belief in the Copenhagen interpretation in the first place. Feynman’s argument already shows the plausibility of the Uncertainty Principle being ontological (which Con essentially dropped based on a misunderstanding).

We've hit some deep waters in this debate, so I'm afraid I won't be able to answer every single point presented, but I'll make my best effort to get to the most important parts.

Contention 1

There isn’t a single part in my round where I stated that hidden variable theories are unfalsifiable. My contention states that Bohm’s mechanics can only be falsified if the rest of quantum mechanics goes down with it. I never wrote that Bohm’s mechanics is unfalsifiable, but that quantum mechanics would also be false if an experiment disproved Bohm’s theory. I have no idea as to where RT received the impression that I consider Bohm’s mechanics to be unfalsifiable.

RT does cite some specific arguments, but the fact that alternative interpretations exist does not undermine the consensus in physics that Bohm's mechanics makes the same predictions as standard quantum mechanics. On top of my already existing sources, I could have cited Fiscaletti [1], Licata [2], Hemmick and Shakur [3], as well as Sole [4], to name a few. Simply put, the mere fact that outliers in the physics community exist shouldn't lead us to doubt the consensus. (Some may ask about RT's poll given the consensus I'm arguing for. The answer is that most objections to Bohm's mechanics were philosophical rather than empirical [5]).

The quote RT provides is not even from Ilja Schmelzer. The article he cites in source two was written by Ilja Schmelzer, but the text provided by RT is actually Schmelzer quoting someone else. This was someone else was the physicist Lubos Motl, who Schmelzerer calls "lumo". He even introduces the text RT quoted by stating "this is also the point where lumo went wrong". It's not a quote from Schmelzer, but Schmelzer quoting Motl in order to criticize his arguments.

This is where things get ironic. The second citation from RT is an article by Schmelzer critizing Motl's argument that Bohm's mechanics contradicts obserable facts and does not make the same predictions as QTF. RT's source, therefore, actually serves to help my first contention! Thanks! Furthermore, as the Stanford Encyclopedia of Philosophy notes, "This is not an objection to Bohmian mechanics but merely a recognition that quantum field theory explains a great deal more than does nonrelativistic quantum mechanics, whether in orthodox or Bohmian form." [6]

Even if I granted that there are slight differences in experiment between Bohm's mechanics and standard quantum mechanics, some of these seem to help Bohm's mechanics rather than refute it. As the Stanford Encyclopedia of Philosophy notes once more: "It is perhaps worth mentioning that despite the empirical equivalence between Bohmian mechanics and orthodox quantum theory, there are a variety of experiments and experimental issues that don't fit comfortably within the standard quantum formalism but are easily handled by Bohmian mechanics. Among these are dwell and tunneling times (Leavens 1996), escape times and escape positions (Daumer et al. 1997a), scattering theory (Dürr et al., 2000), and quantum chaos (Cushing 1994, Dürr et al., 1992a).". [7]

Contention 2

RT tried to use violations of Legget's inequalities against Bohm's mechanics. However, as it was noted by his own source, Bohm's mechanics has nothing to do with Legget's inequalities. I understand that he impied that there were loopholes to this experiment, but the Bohmian doesn't even need to use these loopholes to respond to the argument. We simply have to note that Bohm's mechanics and Legget's inequalities are very different things. In the words of Anthony Legget himself (who is not a Bohmian, and criticizes Bohm), "The original paper is Foundations of Physics 33,1469.What it actually shows is that no theory of the class defined there as "crypto-nonlocal" (CN)(a subclass of the more general class of nonlocal theories) can reproduce all the predictions of QM; and since the predictions of the Bohmian pilot wave model (at least in its later incarnations in the hands of Goldstein,Hiley et al.) are by construction identical to those of QM, it presumably cannot reproduce the predictions of that model either. (so the latter must violate the subsidiary condition defining the CN subclass,though exactly how deserves further investigation). However, recent experiments have shown the class of CN theories to be invalid, and are consistent with QM, hence also with the (neo-)Bohmian model." [8] Bohmians don't need loopholes because there is nothing to get around.

There is more that goes unexplained here. Why do correlations across time refute my argument? RT never explains this vital assumption, so there's not much to answer.

RT uses Earman's symmetry principles to try and prove that space and time must be in one continuum, and therefore Minkowski space is real. This argument is circular, because his symmetry principles actually assume a space-time ontology. As Einstien, Relativity, and Absolute Simultaneity notes, "Earman's principles presuppose a space-time ontology and therefore cannot be employed to justify a space-time interpretation of the formalism of SR over a Lorentzian space and time interpretation." [9]

(Note that Suarez's experiment deals with Legget's inequalities as well, so all of this special relativity talk isn't exactly pertinent, as it falls under the same criticisms offered in regards to other experiments on Legget.)

RT has failed to explain why anything in Feynman's thought experiment entails an ontology. Even if it were impossible to measure position and velocity simultaneously, that doesn't entail anything about ontology. Rather, it would just mean absolute position and velocity are outside of measurement, which is an epistemological concern with how we come to know position and velocity, not what position and velocity are. As an analogy, it may be impossible to conclude with certainty who fired the first shots at Lexington and Concord, but this doesn't imply that nobody fired the first shot. Saying that the impossibility of measuring position and velocity simultaneously entails the ontological claim that they don't exist until measurement is rather like saying that the impossibility of finding out who fired the first shots entails that nobody fired the first shots.

There is nothing about Bohm's mechanics which requires anyone to be able to measure position and velocity simultaneously, so this argument goes nowhere. As I cited earlier, Bohm himself agreed that in an experiment, you can't determine position and velocity simultaneously.

In my last round, I defined an ad hoc hypothesis, and then asked RT to present one example of Bohmian mechanics being changed to fit the data. So far, no such examples have been provided. His analogy to evolution and fossils is more or less an opinion piece, because there is no evidence or sources presented that Bohm's mechanics requires anything that he says it does.

It's not that I haven't sufficiently refuted RT's argument; It's that RT hasn't given a sufficient argument. It's too vague for me to make any constructive comments, which is why I asked for more explanation in the last round. What hidden variables is he talking about? Local, non-local? How does his specific definitions of hidden variable relate to Bohm's mechanics? By reading the actual source, the only thing I can get from the lecture is that it's impossible to measure position and velocity simultaneously ("'If we could look more closely at the electron, we could be able to tell where it would end up.”So far as we know, that is impossible."), which isn't inconsistent with anything Bohm ever said.

Again, simplicity seems to favor Bohm's mechanics in this case. Even though a Copenhagenist may argue that a non-conscious observer collapses the wavefunction, it's not intuitive to our ideas on reality that the moon's existence is dependent on interactions with classical systems. We can ask, "Do you really think the moon isn't there if classical systems aren't interacting with it?". All forms of the Copenhagen interpretation have complementarity [10]. The counterintuitive nature is noted by Hiesmayr and Huber: "[Complemenarity] captures the most counterintuitive difference of a classical and a quantum world". [11] Bohm's mechanics doesn't comitt us to this ontology, so it gives it an advantage over standard orthodox quantum mechanics philosophically.

I'm also not sure what prima facie case was offered by RT. Was he referring to his opening poll on physicists and their favorite interpretation of quantum mechancis? If so, I hardly see this as a prime facie case. Polling 14 physicists in a conference hardly gives the anti-Bohmians a bad start. Furthermore, RT states that he doubts the poll would be different if a larger amount of physicists were asked. This is just downright absurd; I certainly think that more than 0% of physicists would take Bohm's, a modal interpretation, the consistent histories interpretation, or the transactional interpretation.

I urge readers to take note of the fact that 95% of this debate on Con's side revolves around him trying to undermine my case. It is clear Con is barely making any effort to uphold his burden of proof in the debate. **Contention 1 From Con**

*I put the name "Ilja Schmelzer" (who did disagree with the quote, but who also may or may not have sufficient credentials) beside the one quote, instead of the known theoretical physicist's name "Luboš Motl" in my last round by accident.*

If the reality of the collapse of the wave-function was confirmed tomorrow; Bohm mechanics would be falsified. The Copenhagen interpretation wouldn't be falsified as it doesn't predict a non-real collapse. Scientists are getting closer and closer to confirming the reality of the wave-function collapse all the time. Physicist Kater Murch and his team actually captured the collapse process in slow motion[1]. To deny potentially ground breaking experiments that can determine interpretations (such as the one proposed by P. R Holland where we can distinguish between interpretations) due to the fact that harms the "status quo" is amazingly anti-scientific. We never would have known The Big Bang happened if nobody challenged the Steady State universe perspective. Sargon obviously isn't aware that challenging norms is a good thing in science, and hand-waving is not. Here is another physicist that disagrees with Con:

"According to the de Broglie-Bohm theory, the mass and charge of an electron are localized in a position where its Bohmian particle is. However, protective measurement indicates that they are not localized in one position but distributed throughout space." - Shan Gao[2]

This is known as the Distribution Problem (which is fatal to Bohmian mechanics, as it shows Bohmian mechanics is not consistent with measurement). Not only do scientists believe that Bohmian mechanics can be ruled out without ruling out other interpretations, but many scientists believe it already is ruled out without ruling out other interpretations. I can quote many more than just Shan Gao (like Con posted more in his last round), but I have limited space.

Now, Con claims he never implied that hidden variable theories were unfalsifiable, just if that they were falsified; the rest of Quantum Mechanics would be too. That is the most outrageous thing I have heard from Con this entire debate. The Copenhagen interpretation doesn't predict any "hidden variables" tinkering around with experiments. So, how would ruling out hidden variable theories specifically, rule out the Copenhagen interpretation? It wouldn't.

As far as the end of this section with regards to my opponent's last round is concerned, the tunneling times issue has been addressed by M. Abolhasani and M. Golshani in the paper "The Best Copenhagen Tunneling Times"[3]. Vladimir K. Ignatovich modified Scattering Theory to be consistent with standard interpretations of Quantum Mechanics[4]. David Poulin also discusses in his paper "A Rough Guide to Quantum Chaos" how "Chaos" fits with standard Quantum Mechanics[5].

**Contention 2 From Con**

.Violations In Leggett’s Inequalities

I have no problem conceding that violations in Leggett's inequalities do not harm Bohmian mechanics directly. Thus, it seems as if Con wasted his time trying to drive this point home.

.Quantum Erasure With Causally Disconnected Choice

I thought the other experiment by E. Megidish, A. Halevy, T. Shacham, T. Dvir, L. Dovrat, and H. S. Eisenberg[6] shows pretty clearly why my opponent's argument fails. But, I will explain. The experiment proving quantum entanglement across time shows that there need not be any actual instantaneous action. Since this instantaneous action is apparently what apparently makes Minkowskian spacetime impossible; Con's argument is refuted. Simple.

Con only responds to one of my arguments for Minkowskian spacetime; I had two:

(i) The universality pertaining to the behavior of the rod

(ii) Its negation violates the symmetry principles of Earman

Con only responded to (ii); not (i). Therefore, even if his rebuttal goes through; my other argument stands. Either way, Con claims that the symmetry principles of Earman presuppose spacetime. Therefore, it cannot be used to support spacetime. The problem is that the Neo-Lorentzian view of Relativity (which my opponent was trying to support via the Alain Aspect experiments) does presuppose spacetime (neo-Lorentzian spacetime[7]). There are different spacetimes (such as Minkowskian, or Neo-Lorentzian). Yuri Balashov and Michael Janson write:

"[T]he neo-Lorentzian interpretation violates the symmetry principles of Earman , which state that every symmetry of the spacetime posited by a theory should be a symmetry of that theory’s dynamical laws and vice versa." - Yuri Balashov and Michael Janson[8]

This argument doesn't presuppose Minkowskian spacetime, just some spacetime. Thus, it is not clear that this is circular reasoning at all. Con's objection is refuted.

---

My opponent completely drops my argument that the chief result from the "Quantum Erasure With Causally Disconnected Choice" paper[9] doesn't depend on interpretations of Special Relativity.

They show that any non-local "hidden variables" would have to "know" what choices the experimenter would choose before the experiment took place, and change the quantum states accordingly. That is impossible (or at least we know of no laws of physics which could potentially even make that possible). Thus, we should reject hidden variable theories like Bohm's due to this fact.

.Feyman's Argument

As far as Feyman's argument about hidden variables being incompatible with observation: Con completely drops the argument again! The argument shows that the assumption that there are hidden variables does not agree with observation. Con is going on about the other part of it pertaining to how it doesn't show that the Uncertainty Principle is ontological. Even if that is true (which I don't think it is), Feyman's argument still shows that hidden variables do not agree with observation. Since Bohmian mechanics is a hidden variable theory; Feyman's argument shows Bohmian mechanics is flawed.

Con must not just attack the notion that:

(i) Feynman's argument shows the Uncertainty Principle is ontological

but also:

(ii) Feynman's argument shows that the assumption that there are hidden variables disagrees with observation

Con is attacking (i) while ignoring (ii) (which is the most important thing he has to attack). Until he attacks the part of Feynman's argument that really matters; it stands. I'll restate the argument again:

"Imagine that there are hidden variables(non-local), and that an electron in some experiment has some internal variables that are not known, which determine the electron's trajectory given a set of initial conditions (similar to how it is in classical mechanics). However, since these hidden variables are not observed, grouping it with a classical system would entail that the effect was not changed. If these inner variables force the electron to go through the upper slit and land at a certain place on the opposite screen, and some other location for the lower screen, then the probability must necessarily be the sum of two Gaussian like peaks: which self-evidently doesn't agree with observation (as shown by the diagram)" - Me

Even if this fails to show that the Uncertainty Principle is ontological, it succeeds in falsifying hidden variables. Since that is all that is needed to establish the resolution, then Con focusing on whether the Uncertainty Principle is epistemological or not, instead of the fact that the argument falsifies Bohmian Mechanics (but not other interpretations); is a red-herring.

.Occam's Razor And Ad Hocness

Quantum Mechanics is indeterministic prima facie due to apparent wave-function collapse and virtual particle fluctuations. The only way to get determinism out of quantum mechanics is to do some serious stretching; one has to make wild assumptions. Standard quantum mechanics does not assume that there are non-local hidden variables making it look "as if" there is indeterminacy. It is simpler; it just posits indeterminacy. Bohmian Mechanics violates Occam's Razor by positing non-local "hidden variables" that tinker around with experiments. That is not needed to explain the data; hidden variable theories should be rejected. It is as bad as saying their are hidden fairies making it look "as if" there is gravity.

**Contention 3 From Con**

Con still has not presented an argument in favor of the notion that Bohmian mechanics is probably true!

The Copenhagen interpretation being false wouldn't mean that Bohmian mechanics is probably true. The Copenhagan interpretation being false would support other non-copenhagen interpretations just as much as Bohm's.

Also, "counter-intuitiveness" isn't a good argument. If that's the only argument Con has against the Copenhagen interpretation; this isn't good for him ("hidden variables" messing with experiments is counter-intuitive as well).

It is counter-intuitive that the Sun doesn't rise up and go down, but it doesn't (the Earth goes around the Sun). Science is filled with counter-intuitive notions. We should expect this at the quantum scale.

**Conclusion**

Con dropped my most important arguments, attacked my least important arguments, and presented no argument to support his burden of proof in this debate.

This round will be an explanation of why you should vote Con, an a refutation of some earlier points brought up. Given this, it will not be a point by point refutation like other rounds have brought us.

Conduct and Sources

I've come to the realiziation that RT's argument from Richard Feynman is actually plagiarizing another source. All he did was take a 2011 post on a physics website and change the wording up to make it less obvious. Simply read the text of the page, and compare it to RT's opening statement, and this will become obvious and apparent.

"Let us say that the electron has some internal variables as yet unknown which determine its trajectory given a set of initial conditions just like in classical mechanics. But since these hidden variables are unobserved, coupling it with a classical system should make their effect unchanged. This is what Feynman says, I think, in the last paragraph of Ch1 Vol 3, that if in the double slit experiment, if these inner variables dictate that the electron goes through the upper slit and land at a particular place on the opposite screen, and some other place for the lower screen, then the probability must neccesarily be the sum of two Gaussian like peaks, which does not agree with experiment. " Physics website from 2011 [1]

"Imagine that there are hidden variables, and that an electron in some experiment has some internal variables that are not known, which determine the electron's trajectory given a set of initial conditions (similar to how it is in classical mechanics). However, since these hidden variables are not observed, grouping it with a classical system would entail that the effect was not changed. If these inner variables force the electron to go through the upper slit and land at a certain place on the opposite screen, and some other location for the lower screen, then the probability must neccesarily be the sum of two Gaussian like peaks: which self-evidently doesn't agree with observation." -RT opening round

This a typical type of plagiarism where a text and is taken, a few words are changed around, and then the person tries to pass it off as their own without any citation. Plagiarism is a very bad offense, so this warrants a loss of conduct points.Pro should lose this source point in this debate Although we both had numerous sources, his application of them was flawed. For example, he cited experiments by Zeilinger in 2007 and Suarez in 2008, claiming that they hurt Bohmian mechanics by falsifying Legget-inequalities. By quoting from the papers themselves, it was demonstrated that Legget inequalities had nothing to do with Bohmian mechanics, and this point was conceded by Pro. This shows a misapplication of sources because if he had read the whole thing, he would have realized that the experiments didn't have any implications on Bohmian mechanics. Furthermore, he misattributes a quote from Lubos Motl to Ilja Schmelzer, and his own citation ironically presents an argument for Bohmian mechanics.This demonstrates a clear and obvious misuse of sources. As far as I read, no similar error in my argument was pointed out by Pro. This is why I should get source and conduct points.

Arguments

I want to begin by stating that I've definitely made an effort to uphold my burden of proof in this debate. I made the argument that Bohm's mechanics is simpler due to its intuitive ontology. I made the argument that Bohmian mechanics doesn't rely on a flawed verificationist philosophy of science. I mentioned experiments which favor the Bohmian interpretation when it comes to dwell and tunneling times, escape times and escape positions, scatting theory, and quantum chaos. These all serve to establish the plausibility of Bohmian mechanics.

In my opening round, I stated that "This makes it fundamentally impossible to falsify Bohm’s mechanics without getting rid of QM itself." Pro tried to switch this around to suggest that I "admit[s] that [my]“hidden variable” theory is unfalsifiable". As I pointed out this, this is taking my words out of context in order to make an argument. I didn't ever say that hidden variables were unfalsfiiable, just that you would falsify the rest of QM if you falsified hidden variables. Perhaps Pro thinks that statement is absurd, but that's neither here nor there to what I actually said in this debate. The fact of the matter is that I never said anything close to what Pro argued I said. This continues when Pro states that "To deny potentially ground breaking experiments that can determine interpretations (such as the one proposed by P. R Holland where we can distinguish between interpretations) due to the fact that harms the "status quo" is amazingly anti-scientific." Did I ever say that we should ignore experiments because it harms the status quo? No, I simply suggested that quoting some physicists wasn't sufficient on its own to override the consensus on an issue.

Here's where the irony meter almost explodes; In his opening round, Pro criticized Bohmian mechanics on the grounds that it had little acceptance in physics. Now, he's telling me that I "obviously [aren't] aware that challenging norms is a good thing in science". The very person who argued against Bohmian mechanics based on its unpopularity is telling me that it's a good thing to question norms in science? That's very interesting.

RT argues that the quantum erasure experiment doesn't depend on any interpretation of special relativity because of a quote he offered which said that no naive realist interpretation is consistent. However, Zeilinger is clearly referring to relativistic interpretations of quantum mechanics, because his only argument against a quantum system appearing as either a wave of a particle before measurement is the relativistic assumption that nothing goes faster than speed of light. His quote is better read as "No relativistic interpretation of QM is consistent with our results". However, and RT even agreed to this, Bohmian mechanics is nonrelativistic because it entails a preferred reference frame. The quote, therefore, doesn't establish that Bohmian mechanics is inconsistent with the result.

By rod, I think RT is making the argument that length contraction is proof of Minkowski space. . However, there is a Neo-Lorentzian explanation of time dilation: 'By characterizing the variables for moving frames as effective variables, Lorentz maintained that the real spatial lengths, heights, and widths, and real time, existed only in the absolute reference frame. But omitting the Galilean equation, Einstein's theory lost this causal explanatory power. The coordinates (and all properties) of his inertial reference frames become 'brute facts'." [2] So, not only is time dilation consistent with my argument, but it actually helps.

RT admits that Earman's symmetry principles presuppose "some space-time". This is an implicit concession that he's using the assumption of space-time to establish that space and time are connected. Remember, he used these principles to argue against the idea that "space and time are not married in reality". So, his argument is saying "Space and time are united because of principles which presuppose space and time are united".

Pro cites a paper by Vladimir K. Ignatovichw which helps my argument in some way, because it admits that Copenhagen and non-Bohmian interpretations are not consistent with standard scattering theory. He uses it as an argument because it modifies standard scattering theory to be consistent with Copenhagen and non-Bohmian interpretations. It's an attempt at modifying known facts because it's inconsistent with your hypothesis, which is the same thing Pro has been trying to criticize Bohmian mechanics for this entire debate.

I've been begging Pro to explain why Feynman's experiments entail an ontology, and he's never came through. Even if it's impossible to determine position and velocity simulataneously, this doesn't entail an ontology, just like our inability to determine who shot the first bullet at Lexington and Concord doesn't mean a first shot was never fired. Pro insists that Feynman's experiments disprove hidden variables, but he's failed to articulate himself. There are two types of hidden variables: non-local, and local. Bohm's mechanics is only a non-local hidden variable theory. Pro hasn't explained which type of hidden variables Feynman was talking about, so his argument doesn't establish anything. He could have been talking about local hidden variables, non-local hidden variables, or both. The only way for Feynman's lecture to hurt Bohmian mechanics is if he was attacking non-local hidden variables, but we don't know if he was considering RT's lack of explanation. (Personally, I get the feeling that RT doesn't know either, considering he plagiarized.)

My argument about counterintuitive reasons means that absent of any overriding reason to doubt our intuition, we should accept our basic instincts about reality. Arguments about the sun, therefore, are not analagous. RT's statement that hidden variables are counterinutitive doesn't seen to make any sense, considering that Bohm's mechanics more or less conforms to our everyday intuitions about reality. When I was a Copenhagenist, I tried explaining quantum indeterminism to a friend of mine, who knew nothing about David Bohm, and he asked "Doesn't this just show that you don't know what's causing it, but there could be something outside of the experiment that you dont' know about?". I would hardly consider hidden variables to be counterintuitive if somebody who has never studied quantum mechanics suggests them. Furthermore, RT never explains why factors affecting an experiment that you don't know about are counterintuitive. Such a scenaro is perfectly imaginable to the human mind.

Technically that's still plagiarism. Coincidentally, I took a quiz in my honors English class today, and this very question came up (Is it still plagiarism if you change the words and don't cite the original souce?).

I saw the post and thought that if I changed the words sufficiently, then it would be different enough for it not to be considered plagarism. (I never tried to pass the argument off as my own, I always said they were Feynan's ideas from the beginning).

Reasons for voting decision: Wow. Good job to both in explaining such complicated subjects. A major part of this debate hinged on whether Bohmian mechanics (BM) is consistent with experimental evidence. If it's not, then Pro obviously wins. If it is, then we have to consider Con's argument that we should prefer BM because it's less counter-intuitive than other interpretations and Pro's argument from Okham's razor. I could not get to the bottom of whether BM was consistent with experimental evidence or not. For that reason, I have to tie them on arguments. I gave conduct to Con because he showed that Pro plagarized. I also gave sources to Con because he was able to undermine a few of Pro's sources, showing that Pro took them out of context or misapplied them. I can't help but admire Con a little for going to the trouble of reading them and discovering Pro's errors.

Reasons for voting decision: http://physics.stackexchange.com/questions/7112/why-do-people-still-talk-about-bohmian-mechanics-hidden-variables
Entire ending argument was plagiarized from this. Con rightfully printed it out, the words were just interchanged to make it look better.

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